Devices of this general type are used during technical cytological interventions. By the concept "cytological technology," we mean the investigation and handling of individual animal, plant or bacteria cells or of cell cultures, or even of organized cellular structures, in the broad sense. An important practical use is, for example, in pre-natal, pre-implantation diagnosis during which cell samples are taken from embryos and then investigated for the presence of possible genetically caused diseases or in order to determine the gender of the embryo.
The instruments used during technical cytological interventions will be called technical cytological instruments within the framework of this patent application. In this context, these may be especially capillary tubes or pipettes, but also precision pricking or cutting instruments or electrodes, depending upon the desired practical use.
A typical technical cytological intervention is for instance as follows:
The cellular material that is to be treated--an embryo, for example--is placed in a drop of culture medium in a Petrie dish and coated over with a layer of oil. The cellular material is then bonded, for example, with a retaining capillary tube and on the tube opening by vacuum. Under microscopic examination an acid culture solution is applied to the cell wall of the embryo using an additional capillary tube (the etching capillary) and in this way a hole is etched in the wall. The etching capillary tube is then removed and a blastomere is removed from the embryo using an additional capillary tube (a biopsy capillary) through the hole which was made in the wall of the cell.
Technical cytological interventions are usually performed under optical inspection using a powerful magnifying microscope during which the operator has only a very restricted field of vision available to him. One problem that arises during the exchange of instruments--for example, the exchange of the etching and biopsy capillaries mentioned above--is that, depending on the circumstances, the instrument which one wishes to use next may not be located in the user's field of vision, and the process of re-locating and adjusting its free end in the focal plane of the user's field of vision is relatively time consuming one.
Generally, such devices are thus equipped, for example, with a holder base which provides a separate, moveable holder for each instrument. Each of the holders is coupled to a drive which can shift it from a resting to a working position. Before beginning an intervention, the holder base which is outfitted with the instruments is macroscopically pre-adjusted, and then each of its holders is precisely adjusted by means of set screws, for example, until in the working position the free ends of the instruments mounted in the holders are mapped into the field of vision of the microscope. In this way it is made certain that--while a specific holder is being shifted into the working position--the free end of the instrument held in the selected holder is automatically placed into the operator's field of vision and thereby in direct proximity to the cellular material to be treated, and that it does not have to be re-adjusted by the operator each time in a time-consuming process.
In the working position, the free end of an instrument that is directly engaged in the examination is located on the same plane as, and in direct proximity to, the cell to be treated. Thereafter, the free end of a hollow needle or of any other instrument, for example, can be brought into the desired position on the surface of the cell by positioning the Petrie dish or even the holder base.
As noted above, the holders can be switched between the working position, which has been explained above, and a resting position. The resting position now especially needs to be selected and engaged when the samples of cellular materials that have to be processed are being exchanged. In the majority of cases several such samples are arranged either in a row or else even randomly placed on a Petrie dish. When changing over between two samples, the Petrie dish is positioned until the desired sample has been aligned in the field of vision of the microscope. While this is being done, one needs to make sure that none of the instruments (or of the holders containing the instruments) is set in the working position, i.e., with its free end located on the same level as the cellular material, because this would create the danger that the instrument might damage the cellular material during the largely uncontrolled movement of the Petrie dish.
For this reason, the invention provides for the drives being able to shift the holders not only into a defined working position, but also being able to shift the holders out of this position and into a defined resting position. In the resting position the instruments are aligned in such a way as to guarantee that a sufficiently safe distance to the biological material on the Petrie dish is maintained so that the Petrie dish can be moved along with the microscope table without danger and without extensive optical inspection.
In conventional holder bases, each holder has to be activated separately in order to shift its position. If, for example, it is desired to switch the etching capillary tube from its working position into a resting position, then the corresponding holder must be activated in a suitable way, for example, pneumatically, electrically or in some other way. A separate activation is required once again if, on the return swing, the hollow biopsy needle is supposed to be shifted out of its resting position and into a working position. It is, hence, necessary to have considered precisely beforehand which holder has to be activated and how it has to be activated, especially when several hollow needles are being exchanged between the resting and the working positions. This is a relatively burdensome process for the operator and, especially in the case of lengthy interventions, it can result in undesirable operator errors because of decreased concentration. At a minimum, these operator errors cost time but they also can possibly damage the cellular material.